Search

We report abrupt Te doping of GaInP solar cells grown by molecular beam epitaxy (MBE) through the use of a low substrate temperature of 420 °C and subsequent elimination of surface segregation. First, a Te surface pre-dose layer and reduced substrate temperature were required to achieve abrupt profiles at doping >1 × 1018 cm−3 in calibration samples, while reduced doping of 5.7 × 1017 cm−3 did not require the surface layer. Next, we demonstrate front-junction n+/p GaInP cells with an improved internal quantum efficiency (IQE) after Te doping of the n-type emitter directly attributable to an ∼2.5× higher carrier diffusion length, with IQE-derived short-circuit current density increasing from 13.2 to 14.1 mA/cm2. Rapid thermal annealing further boosted the performance through improvements in the minority carrier lifetime of the p-GaInP base. The use of low substrate temperature in MBE-grown GaInP enables abrupt Te doping profiles to be attained in a straightforward manner and is promising for both solar cells and tunnel junctions. [ABSTRACT FROM AUTHOR]

III-V lasers based on self-assembled quantum dots (QDs) have attracted widespread interest due to their unique characteristics, including low threshold current density (Jth), low sensitivity to backreflections, and resistance to threading dislocations. While most work to date has focused on 1.3 μm InAs/GaAs QDs, InP QDs have also aroused interest in lasers emitting at visible wavelengths. Molecular beam epitaxy (MBE) enables the growth of high-density InP/AlGaInP QDs on exact (001)-oriented GaAs substrates but requires a relatively low substrate temperature of <500 °C. The low substrate temperature used for phosphide growth in MBE leads to degraded optical properties and makes post-growth annealing a crucial step to improve the optical quality. Here, we report the exceptional thermal stability of InP/AlGaInP QDs grown using MBE, with up to 50× improvement in room temperature photoluminescence intensity with the optimization of annealing temperature and time. We also demonstrate the room temperature pulsed operation of InP multiple quantum dot (MQD) lasers on GaAs (001) emitting close to 735 nm with Jth values of 499 A/cm2 after annealing, a factor of 6 lower than their as-grown counterparts and comparable to such devices grown by MOCVD. In0.6Ga0.4P single quantum well (SQW) lasers on GaAs (001) also exhibit a substantial reduction in Jth from 340 A/cm2 as-grown to 200 A/cm2 after annealing, emitting at 680 nm under pulsed operation conditions. This work shows that post-growth annealing is essential for realizing record-performance phosphide lasers on GaAs grown by MBE for applications in visible photonics. [ABSTRACT FROM AUTHOR]

Music is an integral part of culture and human societies, which anthropologists study. What makes music so potent is its ability to contain values, reflect perspectives, and fill niches of societal needs. In this paper, I will discuss how ethnomusicology aids scholars in a deeper understanding of contexts, perspectives, and values in music and the experiences of the people who created it. I will analyze the relationships between music and technique, ritual, and religion in seven case studies. Drawing from examples from "right" singing in Estonia, the choral works of Stravinsky, Ambonwari rituals, ritual wailing in Amerindian Brazil, the maqam, syncretism in Southeast Asia, and Tamil Christian religious music, I will show how ethnomusicology uncovers understanding of the cosmology, values, and socio-cultural interactions of a people and their culture. [ABSTRACT FROM AUTHOR]

Deep learning (DL) models for medical image classification frequently struggle to generalize to data from outside institutions. Additional clinical data are also rarely collected to comprehensively assess and understand model performance amongst subgroups. Following the development of a single-center model to identify the lung sliding artifact on lung ultrasound (LUS), we pursued a validation strategy using external LUS data. As annotated LUS data are relatively scarce—compared to other medical imaging data—we adopted a novel technique to optimize the use of limited external data to improve model generalizability. Externally acquired LUS data from three tertiary care centers, totaling 641 clips from 238 patients, were used to assess the baseline generalizability of our lung sliding model. We then employed our novel Threshold-Aware Accumulative Fine-Tuning (TAAFT) method to fine-tune the baseline model and determine the minimum amount of data required to achieve predefined performance goals. A subgroup analysis was also performed and Grad-CAM++ explanations were examined. The final model was fine-tuned on one-third of the external dataset to achieve 0.917 sensitivity, 0.817 specificity, and 0.920 area under the receiver operator characteristic curve (AUC) on the external validation dataset, exceeding our predefined performance goals. Subgroup analyses identified LUS characteristics that most greatly challenged the model's performance. Grad-CAM++ saliency maps highlighted clinically relevant regions on M-mode images. We report a multicenter study that exploits limited available external data to improve the generalizability and performance of our lung sliding model while identifying poorly performing subgroups to inform future iterative improvements. This approach may contribute to efficiencies for DL researchers working with smaller quantities of external validation data. [ABSTRACT FROM AUTHOR]

We directly show that doping type strongly affects the threading dislocation density (TDD) of relaxed GaP on Si, with n-type GaP having a TDD of ∼3.1 × 107 cm−2, nearly 30× higher than both p-type and unintentionally doped GaP at ∼1.1 × 106 cm−2. Such a high TDD is undesirable since n-GaP on Si serves as the starting point for the growth of epitaxial III-V/Si multi-junction solar cells. After highlighting additional challenges for highly n-doped GaP on Si including increased surface roughness, anisotropic strain relaxation, and inhomogeneous TDD distributions from blocking of the dislocation glide, we go on to show that the TDD of n-GaP on Si rises by 10× as the doping concentration increases from ∼5 × 1016 to ∼2 × 1018 cm−3. Next, we investigate the effects of additional dopant choices on the TDD, determining that electronic effects dominate over solute effects on the dislocation velocity at these concentrations. Finally, we demonstrate the respective roles of compressively strained superlattices, low-temperature initiation, and lowered n-type doping concentration on reducing the TDD for n-GaP on Si. By combining all three, we attain relaxed n-GaP on Si with a TDD of 1.54(±0.20) × 106 cm−2, approaching parity with p-GaP on Si. Such high-quality n-GaP on Si will play an important role in boosting the efficiency of epitaxial III-V/Si multi-junction solar cells. [ABSTRACT FROM AUTHOR]

Pediatric patients and their caregivers often experience perioperative anxiety. Interventions reduce caregiver anxiety improve cooperation and contribute to an improved patient experience. This study seeks to evaluate the efficacy of virtual reality (VR)-assisted mindfulness on perioperative caregiver anxiety. Participants were randomized into a standard of care (SOC) group, which included snacks but no technology-based distractions, or a VR group, which included snacks and a VR-guided meditation. Caregiver anxiety was measured before and after the intervention using the Visual Analogue Scale for Anxiety (VAS-A). Secondary aims explored participants' baseline anxiety with the State-Trait Anxiety Inventory (STAI). VR group participants completed a satisfaction survey. Linear regression models of VAS-A and STAI were used to compare group differences. Satisfaction survey results were reported with descriptive statistics. 26 participants were included, with 12 randomized to the SOC group and 14 to the VR group. VAS-A scores in the VR group were lower than those in the SOC group (p =.002). The STAI found no change in participants' state of anxiety in the SOC group (p =.7108), compared to a significant reduction (p =.014) in the VR group when controlling for anxiety traits. 12 of 14 caregivers in the VR group expressed satisfaction or strong satisfaction. This study supports the implementation of VR mindfulness as a method to reduce caregiver anxiety. VR use in the pediatric healthcare setting is safe and inexpensive, and the intervention had a high degree of participant satisfaction. [ABSTRACT FROM AUTHOR]

Background: Virtual reality (VR) technologies have demonstrated therapeutic usefulness across a variety of health care settings. However, graduate medical education (GME) trainee perspectives on VR acceptability and usability are limited. The behavioral intentions of GME trainees with regard to VR as an anxiolytic tool have not been characterized through a theoretical framework of technology adoption. Objective: The primary aim of this study was to apply a hybrid Technology Acceptance Model (TAM) and a United Theory of Acceptance and Use of Technology (UTAUT) model to evaluate factors that predict the behavioral intentions of GME trainees to use VR for patient anxiolysis. The secondary aim was to assess the reliability of the TAM-UTAUT. Methods: Participants were surveyed in June 2023. GME trainees participated in a VR experience used to reduce perioperative anxiety. Participants then completed a survey evaluating demographics, perceptions, attitudes, environmental factors, and behavioral intentions that influence the adoption of new technologies. Results: In total, 202 of 1540 GME trainees participated. Only 198 participants were included in the final analysis (12.9% participation rate). Perceptions of usefulness, ease of use, and enjoyment; social influence; and facilitating conditions predicted intention to use VR. Age, past use, price willing to pay, and curiosity were less strong predictors of intention to use. All confirmatory factor analysis models demonstrated a good fit. All domain measurements demonstrated acceptable reliability. Conclusions: This TAM-UTAUT demonstrated validity and reliability for predicting the behavioral intentions of GME trainees to use VR as a therapeutic anxiolytic in clinical practice. Social influence and facilitating conditions are modifiable factors that present opportunities to advance VR adoption, such as fostering exposure to new technologies and offering relevant training and social encouragement. Future investigations should study the model's reliability within specialties in different geographic locations. [ABSTRACT FROM AUTHOR]